Effect of Electrolytes on Colloidal Stability

• Effect of Electrolytes on Colloidal Stability explains how ions alter charge, causing coagulation or stability.
• Effect of Electrolytes on Colloidal Stability is key in pharmaceuticals, water treatment, and food systems.
• Electrolytes play a crucial role in determining colloidal stability by influencing the surface charge and electric double layer surrounding colloidal particles.

1. Coagulation and Double Layer Compression

• Electrolyte ions neutralize the surface charge of colloidal particles.
• This leads to:
  • Reduction in zeta potential
  • Compression of the electric double layer
  • Weakened electrostatic repulsion between particles
• Result: Particles come closer together, leading to flocculation (aggregation) or coagulation (precipitation).
• Pharmaceutical relevance:
  • Excessive electrolytes in colloidal drug formulations can lead to instability.
  • In parenteral preparations, this can pose serious risks (e.g., embolism).

2. Schulze–Hardy Rule

• The coagulating power of an electrolyte increases with the valency of the counter-ion.
• Higher-valency ions are more efficient at neutralizing colloidal charges.
  • For negatively charged colloids:
    • Al³⁺ > Ca²⁺ > Na⁺
  • Importance:
    • Helps in predicting and controlling colloidal stability in formulations and industrial processes.

3. Critical Coagulation Concentration (CCC)

• CCC is the minimum concentration of an electrolyte required to cause coagulation of colloidal particles.
• A lower CCC means:
  • Stronger electrolyte effect
  • Greater tendency to destabilize the colloid

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